Typically, a patient's temperature is taken orally, axillary, or rectally. The method chosen is based upon the age and consciousness of the patient. Originally, temperature was measured with a conventional glass and mercury clinical thermometer. Glass and mercury thermometers can be dangerous to use and they require substantial time to reach the patient's actual temperature.
Recently, electronic or digital thermometers have been developed to overcome the shortcomings of conventional glass and mercury clinical thermometers. One type of digital thermometer is a tympanic thermometer, which senses infrared radiation from a patient's ear drum. Tympanic thermometers provide a fast temperature reading, but their accuracy tends not to be as good as conventional clinical thermometers. Another type of digital thermometer includes a temperature sensing probe and circuitry for calculating and displaying the temperature detected by the probe. The probe may be used in the same way as a conventional glass and mercury clinical thermometer to measure oral, axillary, or rectal temperature. The probe type digital thermometers tend to provide accurate temperature readings almost as fast as tympanic thermometers.
Existing clinical thermometers, whether conventional or digital, have certain drawbacks in terms of time and effort on the part of the healthcare professional and inconvenience to the patient. NASA (National Aeronautics and Space Administration) has developed an ingestible thermometer that it uses to monitor the temperature of its astronauts. The NASA thermometer includes a temperature sensor, a transmitter, and a battery encapsulated in a relatively large pill-like structure. The NASA ingestible thermometer transmits the astronaut's temperature periodically to an external receiver. The NASA ingestible thermometer offers certain advantages over conventional thermometers. Temperature is recorded substantially automatically and continuously without inconvenience to monitoring personnel or the subject. However, the NASA ingestible thermometer requires an internal battery, and therefore, is rather large and difficult to swallow, and consequently, nearly impossible for use with children. Moreover, the NASA ingestible thermometer is too expensive to be used in a doctor's office or hospital.